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Opeler
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Discussion Starter · #1 ·
I'm rebuilding the stock 1.9L engine on my blue roadster as that engine is actually 30-35 year old and although it doesn't run bad, it has a lot of blow by and oil leaks. So why not upgrade! Using the same basic formula as I did on my 2.4L to 2.6L, I've come up with a formula to pump the 1.9L to 2.1L. By using VW G60 connecting rods, I can offset the crank stroke and achieve a 73mm stroke from the stock 69.8mm. Then using Porsche 914 96 mm pistons, I achieve a 2.11L displacement. The piston pin height and pin diameter are a perfect match for a zero deck height and the pistons already have the double valve reliefs in them. If the block or head deck need some minor milling, any additional height can be gained using the Cometic head gasket of the proper thickness. So I've got the bottom end figured out.

Next question is the head. I've decided to stick with the OR66 cam which is readily available and use new hydraulic lifters. So given a displacement of 2.1L and an OR66 cam, what valve size would you experts recommend? I don't plan to do any porting other than match the manifolds, gaskets and head openings so they are a clean match.
 

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I have a similar setup that I bought from Ernie Bello many years ago. Stroked crank, custom rods (Honda spec?), and custom racing pistons. I had a block bored out for those pistons but haven't yet gotten around to putting it together.
 

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Opeler
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Discussion Starter · #3 ·
I have a similar setup that I bought from Ernie Bello many years ago. Stroked crank, custom rods (Honda spec?), and custom racing pistons. I had a block bored out for those pistons but haven't yet gotten around to putting it together.
Nice, what was the bore you ended up with? I've many thread which imply you can bore the 1.9 block out to upwards of 97mm but it seems to vary with the condition of the block. I'm hoping I'll be good at 96mm.
 

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Nice, what was the bore you ended up with? I've many thread which imply you can bore the 1.9 block out to upwards of 97mm but it seems to vary with the condition of the block. I'm hoping I'll be good at 96mm.
I don't recall, Mike. I'll try to dig the set out and let you know.
 

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Opeler
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Discussion Starter · #6 ·
What kind of Horse Power rating do you anticipate.......
Have no idea and that's really a huge goal. Number one goal is fixing the oil leaks spewing out of every gasket of this old tired engine. I would imagine it would be on par or a little better than most of the 2 liter big valve builds that are so common.
 
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Have no idea and that's really a huge goal. Number one goal is fixing the oil leaks spewing out of every gasket of this old tired engine. I would imagine it would be on par or a little better than most of the 2 liter big valve builds that are so common.
Personally, if you don't go for bigger valves and a hotter cam I think you'll be disappointed in the power.
 

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I agree and that's my plan. OR66 cam. Just seeking advice on valve sizes.
45 mm intake valves from the 2.4L, and 36mm exhaust valves from the 2L
 
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A general rule of thumb is to expect a torque increase from increased displacement. But not necessarily a power increase (though there is usually some more power from more efficient pumping). In addition, for a given camshaft, a bigger displacement engine will usually hit peak torque numbers at a lower rpm.

Power increases are almost always from improved airflow, although more efficient combustion factors in too…as in from higher compression.

The increased airflow can be from larger induction system, larger exhaust system, better flowing cylinder head, and better camshaft design.

You only need to look at the factory Opel CIH power ratings to see that displacement alone does not factor in for much.

These are European power ratings BTW, as in metric HP, or Pferdestärke. This is about 98.6% of SAE standards.

1.9E - 105 PS/ 103.53 HP
2.0E - 110 PS/ 108.46 HP
2.2E - 115 PS/ 113.39 HP
2.4E - 126 PS/ 124.23 HP

So again, not a huge power disparity, though the bigger engines have a much more driveable power band due to the lower rpm power peak and broader torque delivery.

All that said, if you are planning to install bigger valves and NOT port the head, it’s hardly worth the investment. All you really end up doing is adding valve mass which requires stronger springs which eats HP.

You barely get any flow increase unless SOME work is done with a die-grinder. Less than 10%.
 

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Oh, and lastly, port-matching the head of a CIH to the manifolds does nothing. Zero, NADA, zip!

The intake manifold is smaller than the intake port openings. So there is no reversion problem there. Making them bigger at the head/ intake junction just adds more volume with zero flow increase. There is absolutely nothing to be gained unless the restrictions in the intake plenum, intake runner radius, and intake ports are corrected first. When those are optimized THEN port matching matters.

It may matter on an old Chevy or a Ford, but on an Opel there is zero airflow gained (flowbench proven) and zero power gained (dyno proven).
 
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